Mechanical conveyor systems of a variety of different types and designs are employed for handling production lines in all phases of industry. For example, one area in which conveyor systems are used is in the dip molding of latex or vinyl gloves. For years, as shown in U.S. Pat. Nos. 3,117,341; 3,304,576; 3,369,271; 3,431,596; and 3,570,053, various types of machines have been used to carry work pieces or molds along a path of production steps including dipping into liquid latex or vinyl, rotating and shifting to curing stations to produce the desired shaping and curing, and transporting the product to a stripping location where the gloves or similar products are removed from the mold for use.
Throughout the years various types of conveyors have been employed including the well known types of chain and cable conveyors. One difficulty that occurs with all types of conveying systems is the problem of change in pitch as the cable stretches during use when subjected to loads and handling as the cable runs on a continuous travel path over a prolonged period of time. This is true whether the cable is run at high speeds or at relatively low speeds. At some time the cable will fail and naturally one major consideration in dealing with conveyor systems is longevity and dependability. The major difficulty that occurs when the cable or chain stretches is that the pitch changes between the elements mounted on the cable which must mesh with either idler or drive sprockets. The drive sprockets naturally match with the cable to direct it under power along the desired path. Primarily, the idler sprockets are used to guide the cable and change direction of the cable as it moves along the desired path in the manufacturing system.
As the pitch of the cable changes over a period of time, particularly as the cable lengthens, it reaches a point where it no longer meshes with the drive or idler sprockets causing interference and ultimate failure. The lack of ability to accommodate the change in pitch as the cable stretches during a long period of use sharply reduces cable life and increases the time during which the machine is not in operation.
In conventional chain and cable trolley conveyor practice, vertical idler sprockets are used only in limited ways like dipping the work piece in paint. Also vertical upward bends use the trolley wheels against the track to balance the chain or cable tension, rather than a vertical turn wheel with an interrupted track. Conventional chain and cable conveyors have no provision for inverting the work.
Stock cable trolley conveyors are similar in arrangement to the chain type trolley conveyors with the track on the top, the chain or cable is located fairly close to the lower track and the load or work piece hangs below the chain or cable. The cable trolley conveyor pitches are created by swageing buttons to the cable at the desired pitch. These become a permanent part of the cable and the trolleys fit around these buttons to receive their locations on the cable. While chain trolley conveyors utilize horizontal turn idler wheels to balance the chain tension force resulting from horizontal direction changes, cable trolley conveyors must utilize turn idler sprockets for the same purpose. The chain conveyor idler turn wheels are remarkably long lived, trouble-free components, while the cable conveyor idler sprockets are short lived, troublesome components.
Both conveyor chains and conveyor cables increase in pitch throughout their period of use as discussed above. This fact has no effect on the chain idler turn wheels because they have smooth cylindrical surfaces, but aggravates the problem of proper meshing of the cable trolley brackets in the idler sprocket gaps that are positioned between the cable supoorting shoes.
As discussed, the stock cable conveyor idler sprockets were troublesome components causing frequent cable failures for the lifetime of between 1 and 6 months. Accordingly, there has been clearly a need to provide a cable system which minimizes the change of cable failure for a prolonged period of time materially reduces cable wear, and accommodates cable pitch variation.